Many electronic throttle bodies have a limp home feature, in which a spring or springs force the throttle blade to a nominal high-idle condition in case of loss of control of the throttle valve, such as due to a signal or wiring failure. This spring requires that the throttle valve actuator, such as a motor geared to the throttle plate, apply a force to overcome the spring constant in order to move the throttle valve plate. The sign and amount of force required to move the throttle valve plate changes depending on whether the throttle valve is opening or closing, and depending on which side of the limp home position the throttle valve plate is located.
Additionally, a gear train that connects the motor to the throttle valve may have backlash that causes a delay in response of the throttle valve plate to actuation of the motor. Because teeth of meshed gears in the gear train may not be in tight contact with one another, they may have some play or lash between them, resulting in a delay between when a first gear in the gear train is moved until a second gear having teeth complementary to those of the first gear responds to such movement. Such backlash is most often seen when a switch from loading one side of a gear tooth to an opposite side thereof is required, such as when the gear train is actuated to change the direction of the throttle plate from opening to closing, or vice versa.